Vacuum trucks are well-known and widely used for excavation or extraction of particulate material by vacuum from an area to be cleared, with the material collected being transported through a vacuum hose into a storage tank from which the material is separated from the air before the air enters the vacuum pump.
Such vacuum trucks are commonly used for clearing pipes and other areas where a collection of solid material needs to be extracted from an area containing water. Thus a blocked sewer or drainage pipe contains water which can be returned to the pipe and a quantity of solids which must be removed.
One problem which arises with vacuum trucks of this type is that it is desirable to increase as far as possible the amount of solids which can be collected so as to transport as much as possible of the material which must be removed while returning liquid to the area being cleaned. It will be appreciated that to maximize the amount of material carried in a load reduces the number of loads which must be transported with the potential of significantly reducing total working time to clear a particular area or blockage.
U.S. Pat. No. 5,722,113 (of the present inventor Baziuk) issued Mar. 3, 1998 shows an arrangement for collecting dust and moisture where separate collection tanks are provided on each side of the tank and contain hanging chains which form a screen. There is no disclosure of separation of liquid and solids within the tank.
U.S. Pat. No. 4,016,994 (Wurster) issued Apr. 12, 1977 shows a two tank system for collecting air transportable material which may be wet or dry but does not act to separate the wet from the dry.
U.S. Pat. No. 4,904,126 (Voith) issued Feb. 27, 1990 shows a vacuum truck for collecting primarily dry material which uses filter cartridges to separate the particulate materials from the air.
U.S. Pat. No. 6,453,584 (Buckner) issued Sep. 24, 2002 shows an arrangement in which the collected materials and separated into liquid and solids components using a vibrating screen onto which the material is deposited with the liquid falling through into a separate container. The materials are continually discharged so that the tank is not required as a transport container, thus allowing the separation system to take up a significant part of the tank.
U.S. Pat. No. 6,604,304 (Slabach) issued Aug. 12, 2003 shows a vacuum system with a slurry tank for transporting the extracted slurry material. There is no attempt to separate the liquid and solids content so that the total of the slurry needs to be transported.
U.S. Pat. No. 5,295,317 (Perrott) issued Mar. 2, 1994 shows an excavation machine in which the collected materials and separated into liquid and solids components using a rotating screen. The materials are continually discharged so that the tank is not required as a transport container, thus allowing the separation system to take up a significant part of the tank.